1. Field of the Invention
The invention relates to a method for the non-destructive testing of workpiece surfaces by means of penetrant testing.
2. Discussion of Background Information
Methods for the non-destructive testing of workpiece surfaces are known. In what is termed penetrant testing, a penetrant is applied to a cleaned workpiece surface which is to be examined. The capillary action of fine surface cracks and pores promotes the penetration of the penetrant into such recesses on the workpiece surface. Dye penetrant testing methods use non-fluorescent dye solutions as the penetrant (e.g. “red-white method”). In what is termed fluorescent penetrant testing, use is made of a fluorescent penetrant. After a predetermined time of action, excess penetrant is then washed away in an intermediate cleaning operation. Then, a developer is applied to the workpiece surface which is to be tested. The developer promotes the re-wetting of the penetrant on the recess in the workpiece surface, the developer causing the penetrant to be drawn out of the recess to the surface. As a result, possible irregularities in the workpiece surface, e.g. crack-like material separations, become clearly visible.
Fluorescent penetrant testing is used in particular in aircraft construction, shipbuilding and automotive engineering and also other metalworking industries. However, it is also possible to examine other materials, e.g. ceramic, for corresponding surface cracks and pores.
However, a disadvantage of the known method, in particular when used in aircraft construction, is that, after the application of the developer and the corresponding mapping of the recesses or surface cracks, to verify the display, the corresponding regions of the presumed recesses have to be subjected to manual surface cleaning in order to remove excess penetrant which has been redistributed on the workpiece surface around the region of the recess by the application of the developer. Only after this mechanical cleaning does the penetrant which lines exclusively the recess or the surface crack become visible. An accurate assessment and measurement of the recess are made possible only in this way. However, this manual cleaning step is time-consuming and costly. Moreover, it can be standardized only with difficulty, as a result of which a standardized classification of possible recesses or defects in the workpiece surface is also difficult.
It would be advantageous to have available a method for the non-destructive testing of workpiece surfaces which makes a quicker and less expensive examination of the workpiece surfaces possible.